When to plant potatoes

Potatoes are a cool-season crop that takes a light frost, so it can go out a little before the last frost. Type your town to see the dates for your weather station.

The seed packet, in short

Potato planting dates by zone

Each row uses the typical frost dates of a zone: the middle value among towns of 10,000 people or more in it. In zone 6b, for example, the typical last frost is Apr 20, so the first step for potatoes, plant seed potatoes, falls Mar 9 to Apr 20. Towns in one zone can differ by two weeks, so your own town's dates above are the better guide.

Good to know about potatoes

• Plant pieces of seed potato with at least one good eye each, or small whole seed potatoes; plant soon after cutting.
• Cold, wet soil rots seed pieces, so wait until the soil can be worked and has warmed to about 45 to 50 F. Shoots nipped by a late frost usually regrow.
• Tubers form best with soil at 60 to 70 F and stop forming near 80 F, so early planting matters.
• Depth: 1 to 3 in. when you plan to hill or mulch heavily, 4 to 6 in. for standard planting.

How to plant potatoes

• Grow potatoes in full sun, at least 6 hours a day, in loose, fertile, well-drained soil.
• Cut seed potatoes into chunks of about 1.5 to 2 oz; very small pieces give weaker plants.
• Hill loose soil up around the stems a little at a time as plants grow, starting a few weeks after they come up; this gives tubers room and keeps them out of the light.
• Instead of hilling, you can cover the rows with 4 to 6 in. of loose straw and add more as it settles.
• Keep soil evenly moist, about 1 to 2 in. of water a week, while tubers are forming; dry spells followed by heavy watering cause knobs, cracks and hollow centers.

Types that change the timing

• Potato varieties are grouped as early, mid-season and late; late types are the usual choice for winter storage.
• Within those groups you will find russets, smooth white or yellow-fleshed potatoes, and red-skinned potatoes.

Common mistakes

• Planting grocery-store potatoes or saving your own tubers for seed; store potatoes may be treated to stop sprouting and saved tubers can carry disease, so buy certified seed potatoes.
• Leaving tubers exposed to light by planting too shallow or skipping hilling; they turn green and bitter.
• Hoeing deep or close to the plants, which slices into developing tubers.

When potatoes are ready

• New potatoes can be dug once tubers reach 1 to 2 inches, before the vines die